WASHINGTON (Yonhap) -- A dozen Iranian officials, responsible for the country's ballistic missile program, visited North Korea last week to observe its latest rocket launch, which ended in failure, a diplomatic source here said Sunday.

"On March 31, 12 Iranians of the Shahid Hemmat Industrial Group (SHIG) arrived in North Korea. The Iranians undoubtedly were there to observe the missile launch and receive test data from North Korea," the source told Yonhap News Agency, requesting anonymity.

South Korean government officials neither confirmed nor denied the allegations, citing a practice of not commenting on intelligence-related matter.

SHIG, connected to the Iranian Revolutionary Guard, is a target of U.N and U.S. sanctions.

It is known to have developed the Shahab-3, seen as a replica of North Korea's mid-range Nodong missile using Scud technology, and an upgraded version of Shahab-4 missiles.

North Korea and Iran have long been suspected of regularly exchanging ballistic missile technology.